Thermoplastic air bag covers are now widely used. Examples of such air bag covers can be found in the following U.S. Pat. Nos.: 5,062,661; 5,487,557; 5,465,998; 5,549,323; 5,558,364; 5,498,026; 5,520,412; 5,542,694; and 5,501,485. Snap-on air bag covers are shown in the following U.S. Pat. Nos. from the above list: 5,465,998; 5,498,026; and 5,501,485.
Injection molding apparatus for forming such air bag covers typically have a first mold half having a first molding surface to form a first part of an air bag cover-defining cavity and a second mold half having a second molding surface to form a second complementary part of the air bag cover-defining cavity. The first and second molding surfaces form the air bag cover including a front cover panel and separate resilient clip members integrally formed with the front cover panel. Each of the clip members typically has a front engagement section, a rear shoulder section, and a snap-on groove extending therebetween for snapping the air bag cover onto a retaining member of an air bag assembly.
Typically, the mold parts which form the resilient clip members of the air bag cover are formed to facilitate removal of the air bag cover upon completion of a molding cycle. An operator grabs the molded air bag cover and snaps it off the mold parts forming the clip members. Such manual removal of the air bag cover from the injection molding apparatus is undesirable for many reasons.
U.S. Pat. No. 5,603,968 discloses molding apparatus including a plurality of core members which are movable between retracted and extended positions with respect to one of the movable and fixed mold halves. The core members define a molding cavity along with the movable and fixed mold halves when the core members are in their retracted position.
The core members include a first core member for forming a first projection of the pad which is movable along a predetermined moving path. At least one relatively thin second core member and at least one third core member are also provided. The at least one third core member forms a second projection of the pad. By selectively extending and retracting the core members, the steering wheel pad can be separated from the mold apparatus without requiring an operator to exert manual force therefor.
However, a need still exists for robust injection molding apparatus for molding thermoplastic air bag covers on a production basis.